Memory element and memory device

ABSTRACT

There is disclosed a memory element including a layered structure including a memory layer that has magnetization perpendicular to a film face and a magnetization direction thereof varies corresponding to information; a magnetization-fixed layer that has magnetization that is perpendicular to the film face; and an insulating layer that is provided between the memory layer. An electron that is spin-polarized is injected in a lamination direction of the layered structure, and thereby the magnetization direction of the memory layer varies and a recording of information is performed with respect to the memory layer, a magnitude of an effective diamagnetic field which the memory layer receives is smaller than a saturated magnetization amount of the memory layer, and the memory layer and the magnetization-fixed layer have a film thickness in such a manner that an interface magnetic anisotropy energy becomes larger than a diamagnetic energy.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application claims priority Japanese Priority PatentApplication JP 2010-200983 filed in the Japan Patent Office on Sep. 8,2010, the entire contents of which are hereby incorporated by reference.

BACKGROUND

The present application relates to a memory element that includes amemory layer that stores the magnetization state of a ferromagneticlayer as information and a magnetization-fixed layer in whichmagnetization direction is fixed, and that changes the magnetizationdirection of the memory layer by flowing a current, and a memory devicehaving the memory element.

In an information device such as a computer, a highly dense DRAM thatoperates at a high speed has been widely used as a random access memory.

However, the DRAM is a volatile memory in which information is erasedwhen power is turned off, such that a non-volatile memory in which theinformation is not erased is desirable.

In addition, as a candidate for the non-volatile memory, a magneticrandom access memory (MRAM) in which the information is recorded bymagnetization of a magnetic material has attracted attention andtherefore has been developed.

The MRAM makes a current flow to two kinds of address interconnects (aword line and a bit line) that are substantially perpendicular to eachother, respectively, and inverts the magnetization of a magnetic layerof a magnetic memory element, which is located at an intersection of theaddress interconnects, of the memory device by using a current magneticfield generated from each of the address interconnects, and therebyperforms the recording of information.

A schematic diagram (perspective view) of a general MRAM is shown inFIG. 13.

A drain region 108, a source region 107, and a gate electrode 101, whichmake up a selection transistor that selects each memory cell, are formedat portions separated by an element separation layer 102 of asemiconductor substrate 110 such as a silicon substrate, respectively.

In addition, a word line 105 extending in the front-back direction inthe drawing are provided at an upper side of the gate electrode 101.

The drain region 108 is formed commonly to left and right selectiontransistors in the drawing, and an interconnect 109 is connected to thedrain region 108.

In addition, magnetic memory elements 103, each having a memory layerwhose magnetization direction is inverted, are disposed between the wordline 105 and bit lines 106 that are disposed at an upper side inrelation to the word line 105 and extend in the left-right direction.These magnetic memory elements 103 are configured, for example, by amagnetic tunnel junction element (MTJ element).

In addition, the magnetic memory elements 103 are electrically connectedto the source region 107 through a horizontal bypass line 111 and avertical contact layer 104.

When a current is made to flow to the word line 105 and the bit lines106, a current magnetic field is applied to the magnetic memory element103 and thereby the magnetization direction of the memory layer of themagnetic memory element 103 is inverted, and therefore it is possible toperform the recording of information.

In addition, in regard to a magnetic memory such as the MRAM, it isnecessary for the magnetic layer (memory layer) in which the informationis recorded to have a constant coercive force in order to stably retainthe recorded information.

On the other hand, it is necessary to make a certain amount of currentflow to the address interconnect to order to rewrite the recordedinformation.

However, along with miniaturization of the element making up the MRAM,the address interconnect becomes thin, such that it is difficult to flowa sufficient current.

Therefore, as a configuration capable of realizing magnetizationinversion with a relatively small current, a memory having aconfiguration using magnetization inversion using spin injection hasattracted attention (for example, refer to Japanese Unexamined PatentApplication Publication Nos. 2003-17782 and 2008-227388, and aspecification of U.S. Pat. No. 6,256,223, PHYs. Rev. B, 54.9353 (1996),and J. Magn. Mat., 159, L1 (1996).

Magnetization inversion using the spin injection means in which a spinpolarized electron after passing through a magnetic material is injectedto the other magnetic material, and thereby magnetization inversion iscaused in the other magnetic material.

For example, when a current is made to flow to a giant magnetoresistiveeffect element (GMR element) or a magnetic tunnel junction element (MTJelement) in a direction perpendicular to a film face, the magnetizationdirection of at least a part of the magnetic layer of this element maybe inverted.

In addition, magnetization inversion using spin injection has anadvantage in that even when the element becomes minute, it is possiblerealize magnetization inversion without increasing the current.

A schematic diagram of the memory device having a configuration usingmagnetization inversion using the above-described spin injection isshown in FIGS. 14 and 15. FIG. 14 shows a perspective view, and FIG. 15shows a cross-sectional view.

A drain region 58, a source region 57, and a gate electrode 51 that makeup a selection transistor for the selection of each memory cell areformed, respectively, in a semiconductor substrate 60 such as a siliconsubstrate at portions isolated by an element isolation layer 52. Amongthem, the gate electrode 51 also functions as a word line extending inthe front-back direction in FIG. 14.

The drain region 58 is formed commonly to left and right selectiontransistors in FIG. 14, and an interconnect 59 is connected to the drainregion 58.

A memory element 53 having a memory layer in which a magnetizationdirection is inverted by spin injection is disposed between the sourceregion 57 and bit lines 56 that are disposed in an upper side of thesource region 57 and extend in the left-right direction in FIG. 14.

This memory element 53 is configured by, for example, a magnetic tunneljunction element (MTJ element). The memory element 53 has two magneticlayers 61 and 62. In the two magnetic layers 61 and 62, one sidemagnetic layer is set as a magnetization-fixed layer in which themagnetization direction is fixed, and the other side magnetic layer isset as a magnetization-free layer in which that magnetization directionvaries, that is, a memory layer.

In addition, the memory element 53 is connected to each bit line 56 andthe source region 57 through the upper and lower contact layers 54,respectively. In this manner, when a current is made to flow to thememory element 53, the magnetization direction of the memory layer maybe inverted by spin injection.

In the case of the memory device having a configuration using magneticinversion using this spin injection, it is possible to make thestructure of the device simple compared to the general MRAM shown inFIG. 13, and therefore it has a characteristic in that highdensification becomes possible.

In addition, when magnetization inversion using the spin injection isused, there is an advantage in that even as miniaturization of theelement proceeds, the write current is not increased, compared to thegeneral MRAM performing magnetization inversion using an externalmagnetic field.

SUMMARY

However, in the case of the MRAM, a write interconnect (word line or bitline) is provided separately from the memory element, and the writing ofinformation (recording) is performed using a current magnetic fieldgenerated by flowing a current to the write interconnect. Therefore, itis possible to make a sufficient amount of current necessary for thewriting flow to the write interconnect.

On the other hand, in the memory device having a configuration usingmagnetization inversion using spin injection, it is necessary to invertthe magnetization direction of the memory layer by performing spininjection using a current flowing to the memory element.

Since the writing (recording) of information is performed by directlyflowing a current to the memory element as described above, a memorycell is configured by connecting the memory element to a selectiontransistor to select a memory cell that performs the writing. In thiscase, the current flowing to the memory element is restricted to acurrent magnitude capable of flowing to the selection transistor (asaturation current of the selection transistor).

Therefore, it is necessary to perform writing with a current equal to orless than the saturation current of the selection transistor, andtherefore it is necessary to diminish the current flowing to the memoryelement by improving spin injection efficiency.

In addition, to increase read-out signal strength, it is necessary tosecure a large magnetoresistance change ratio, and to realize this, itis effective to adopt a configuration where an intermediate layer thatcomes into contact with both sides of the memory layer is set as atunnel insulation layer (tunnel barrier layer).

In this way, in a case where the tunnel insulation layer is used as theintermediate layer, the amount of current flowing to the memory elementis restricted to prevent the insulation breakdown of the tunnelinsulation layer. From this viewpoint, it is also necessary to restrictthe current at the time of spin injection.

Since such a current value is proportional to a film thickness of thememory layer and is proportional to the square of the saturationmagnetization of the memory layer, it may be effective to adjust these(film thickness and saturated magnetization) to decrease such a currentvalue (for example, refer to F. J. Albert et al., Appl. Phys. Lett., 77,3809 (2000)).

For example, in F. J. Albert et al., Appl. Phys. Lett., 77, 3809 (2000),the fact that when the amount of magnetization (Ms) of the recordingmaterial is decreased, the current value may be diminished is disclosed.

However, on the other hand, if the information written by the current isnot stored, a non-volatile memory is not realized. That is, it isnecessary to secure a stability (thermal stability) against the thermalfluctuation of the memory layer.

In the case of the memory element using magnetization inversion usingspin injection, since the volume of the memory layer becomes small,simply considered the thermal stability tends to decrease, compared tothe MRAM in the related art.

When the thermal stability of the memory layer is not secured, theinverted magnetization direction re-inverts by heating, and this leadsto writing error.

In addition, in a case where high capacity of the memory element usingmagnetization inversion using the spin injection is advanced, the volumeof the memory element becomes smaller, such that the securing of thethermal stability becomes an important problem.

Therefore, in regard to the memory element using magnetization inversionusing spin injection, thermal stability is a very importantcharacteristic.

Therefore, to realize a memory element having a configuration where themagnetization direction of the memory layer as a memory is inverted byspin injection, it is necessary to diminish the current necessary formagnetization inversion using the spin injection to a value equal to orless than the saturation current of the transistor, and thereby securingthe thermal stability for retaining the written information reliably.

As described above, to diminish the current necessary for magnetizationinversion using spin injection, diminishing the saturated magnetizationamount Ms of the memory layer, or making the memory layer thin may beconsidered. For example, as is the case with U.S. Pat. No. 7,242,045, itis effective to use a material having a small saturated magnetizationamount Ms as the material for the memory layer. However, in this way, ina case where the material having the small saturated magnetizationamount Ms is simply used, it is difficult to secure thermal stabilityfor reliably retaining information.

Therefore, in this disclosure, it is desirable to provide a memoryelement in which the decrease in the write current and the improvementin a thermal stability can be compatible with each other, and a memorydevice with the memory element.

According to an embodiment, there is provided a memory element includinga layered structure including a memory layer that has magnetizationperpendicular to a film face and the magnetization direction thereofvaries corresponding to information, a magnetization-fixed layer thathas magnetization that is perpendicular to the film face and becomes areference for the information stored in the memory layer, an insulatinglayer that is provided between the memory layer and themagnetization-fixed layer and is formed of a non-magnetic material, andan anti-ferromagnetic layer adjacent to the magnetization-fixed layer ata side opposite to the insulating layer side. An electron that isspin-polarized is injected in a lamination direction of the layeredstructure, and thereby the magnetization direction of the memory layervaries and a recording of information is performed with respect to thememory layer, a magnitude of an effective diamagnetic field which thememory layer receives is smaller than a saturated magnetization amountof the memory layer, and the memory layer and the magnetization-fixedlayer have a film thickness in such a manner that an interface magneticanisotropy energy becomes larger than a diamagnetic energy.

Specifically, the film thickness of the memory layer and themagnetization-fixed layer may be a film thickness in which an energybarrier E per unit area, which is expressed by E=Ki−(μ₀·Ms²·t)/2, islarger than zero, that is, E>0. Here, Ki is an interface magneticanisotropy energy per unit area, Ms is a saturated magnetization amount,μ₀ is a space permeability, and t is a film thickness.

In addition, the memory layer may include Co—Fe—B.

In addition, the magnetization-fixed layer may include Co—Fe—B.

According to another embodiment, there is provided a memory deviceincluding a memory element that retains information through themagnetization state of a magnetic material, and two kinds ofinterconnects that intersect each other, wherein the memory element hasthe configuration of the above-described memory element according to theembodiment, the memory element is disposed between the two kinds ofinterconnects, and a current flows to the memory element in thelamination direction through the two kinds of interconnects, and therebya spin-polarized electron is injected to the memory element.

According to the configuration of the memory element of the embodiment,a memory element that retains information through a magnetization stateof a magnetic material is provided, a magnetization-fixed layer isprovided over the memory layer through a intermediate layer, theintermediate layer is formed of an insulating material, an electron thatis spin-polarized is injected in a lamination direction and thereby themagnetization direction of the memory layer is changed and a recordingof information is performed with respect to the memory layer, andtherefore it is possible to perform the recording of the information byflowing a current in the lamination direction and by injecting aspin-polarized electron.

In addition, the magnitude of an effective diamagnetic field which thememory layer receives is smaller than a saturated magnetization amountof the memory layer, such that the diamagnetic field which the memorylayer receives decreases, and therefore it is possible to diminish theamount of the write current necessary for inverting the magnetizationdirection of the memory layer.

On the other hand, it is possible to diminish the amount of the writecurrent even when the saturated magnetization amount of the memory layeris not diminished, such that the saturated magnetization amount of thememory layer becomes sufficient, and it is possible to sufficientlysecure thermal stability of the memory layer.

In addition, the thickness of the memory layer and themagnetization-fixed layer, which are ferromagnetic layers, are designedwith a predetermined range, and thereby a perpendicular magneticanisotropy is applied.

When the film thickness of the ferromagnetic layers is within apredetermined range, the interface magnetic anisotropy energy is largerthan the diamagnetic field energy. At this time, the easy axis ofmagnetization of the ferromagnetic layer becomes perpendicular directionwith respect to a laminated face. Therefore, it is possible to decreasean inversion current of the memory element compared to a case where theeasy axis of the magnetization is an in-plane direction.

In addition, according to the configuration of the memory device of theembodiment, the memory element is disposed between the two kinds ofinterconnects, and a current flows to the memory element in thelamination direction through the two kinds of interconnects, and therebya spin-polarized electron is injected to the memory element. Therefore,it is possible to perform the recording of information by a spininjection by flowing a current in the lamination direction of the memoryelement through the two kinds of interconnects.

In addition, even when the saturated magnetization amount is notdiminished, it is possible to diminish the amount of the write currentof the memory element, such that it is possible to stably retain theinformation recorded in the memory element and it is possible todiminish the power consumption of the memory device.

According to the embodiments, even when the saturated magnetizationamount of the memory layer is not diminished, the amount of the writecurrent of the memory element may be diminished, such that the thermalstability representing the information retaining ability is sufficientlysecured, and it is possible to configure a memory element excellent in acharacteristic balance. Particularly, the memory layer and themagnetization-fixed layer have a film thickness in such a manner that aninterface magnetic anisotropy energy becomes larger than a diamagneticenergy, such that the easy axis of the memory layer and themagnetization-fixed layer become a perpendicular direction with respectto a laminated face. Therefore, it is possible to decrease an inversioncurrent of the memory element compared to a case where the easy axis ofthe magnetization is an in-plane direction.

Therefore, it is possible to realize a memory device that operatesstably with high reliability.

In addition, the write current is diminished, such that it is possibleto diminish power consumption during performing the writing into thememory element. Therefore, it is possible to diminish the powerconsumption of the entire memory device.

Additional features and advantages are described herein, and will beapparent from the following Detailed Description and the figures.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is an explanatory view illustrating a schematic configuration ofa memory device according to an embodiment;

FIG. 2 is a cross-sectional view illustrating a memory element accordingthe embodiment;

FIG. 3 is a diagram illustrating a relationship between an amount of Coof a memory layer of 0.09×0.18 μm size and an inversion current density;

FIG. 4 is a diagram illustrating a relationship between an amount of Coof a memory layer of 0.09×0.18 μm size and an index of thermalstability;

FIG. 5 is a diagram illustrating a relationship between an amount of Coof a memory layer of 50 nm φ size and an index of thermal stability;

FIGS. 6A and 6B are explanatory views illustrating a layer structure anda measurement result of a sample of experiment 5 according to theembodiment;

FIGS. 7A to 7C are explanatory views illustrating a film thicknessdependency by experiment 5 according to the embodiment;

FIGS. 8A and 8B are explanatory views illustrating a layer structure ofa sample of experiment 6 according to the embodiment;

FIGS. 9A and 9B are explanatory views illustrating a measurement resultof experiment 6 according to the embodiment;

FIGS. 10A and 10B are explanatory views illustrating a layer structureand a measurement result of a sample of experiment 7 according to theembodiment;

FIGS. 11A and 11B are explanatory views illustrating a layer structureand a measurement result of a sample of experiment 8 according to theembodiment;

FIG. 12 is an explanatory view illustrating a measurement result ofexperiment 8 according to the embodiment;

FIG. 13 is a perspective view schematically illustrating a configurationof an MRAM in the related art;

FIG. 14 is an explanatory view illustrating a configuration of a memorydevice using a magnetic inversion using a spin injection; and

FIG. 15 is a cross-sectional view of a memory device of FIG. 14.

DETAILED DESCRIPTION

Embodiments of the present application will be described below in detailwith reference to the drawings.

1. Outline of Memory Element of Embodiment

2. Configuration of Embodiment

3. Experiment

1. Outline of Memory Element of Embodiment

First, outline of a memory element of an embodiment according to thepresent disclosure will be described.

The embodiment according to the present disclosure performs therecording of information by inverting a magnetization direction of amemory layer of a memory element by the above-described spin injection.

The memory layer is formed of a magnetic material such as ferromagneticlayer, and retains information through the magnetization state(magnetization direction) of the magnetic material.

It will be described later in detail, but the memory element has alayered structure whose example is shown in FIG. 2, and includes amemory layer 17 and a magnetization-fixed layer 15 as two ferromagneticlayers, and an insulating layer 16 (tunnel insulating layer) as anintermediate layer provided between the two magnetic layers.

Particularly, in the case of the embodiment, the memory layer 17 and themagnetization-fixed layer 15 that are ferromagnetic layers have a filmthickness in such a manner that an interface magnetic anisotropy energybecomes larger than a diamagnetic energy.

The memory layer 17 has magnetization perpendicular to a film face and amagnetization direction varies corresponding to information.

The magnetization-fixed layer 15 has the magnetization that is areference for the information stored in the memory layer 17 and isperpendicular to the film face.

The insulating layer 16 is formed of a non-magnetic material and isprovided between the memory layer 17 and the magnetization-fixed layer15.

Spin-polarized electrons are injected in the lamination direction of alaminated structure having the memory layer 17, the insulating layer 16,and the magnetization-fixed layer 15, and the magnetization direction ofthe memory layer 17 is changed and thereby information is recorded inthe memory layer 17.

A basic operation for inverting the magnetization direction of themagnetic layer (memory layer 17) by the spin injection is to make acurrent of threshold value or greater flow to the memory elementincluding a giant magnetoresistive effect element (GMR element) or atunnel magnetoresistive effect element (MTJ element) in a directionperpendicular to a film face. At this time, the polarity (direction) ofthe current depends on the inverted magnetization direction.

In a case where a current having an absolute value less than thethreshold value is made to flow, magnetization inversion does not occur.

An important problem in a spin injection type magnetic memory iscompatibility between securing thermal stability and the decrease in ainversion current.

A written state may be unintentionally changed due to the magnetizationinversion caused by thermal fluctuation. A frequency of occurrence ofmagnetic inversion due to the thermal fluctuation is described by usingan index Δ of the thermal stability.

In addition, it is preferable that an inversion current Ic₀ necessaryfor spin injection magnetization inversion be small, from the viewpointof power consumption or a cell size.

The index Δ of the thermal stability and the inversion current Ic₀ aredifferent depending on a direction of the easy axis of magnetization ofthe memory layer. Specifically, this difference is as follows. Equations(1) and (2) represent the index Δ and the inversion current Ic₀,respectively, in the case of the in-plane magnetization (the directionof the magnetization is parallel with a film face), and equations (3)and (4) represent the index Δ and the inversion current Ic₀,respectively, in the case of the perpendicular magnetization (thedirection of the magnetization is perpendicular to the film face).

Math.  1 In-plane  magnetization$\Delta = {\frac{KV}{k_{B}T} + {\frac{\mu_{0}{Ms}^{2}V}{2k_{B}T}( {N_{y} - N_{x}} )\mspace{335mu}\text{(1)}}}$$I_{c0} = {( \frac{4{ek}_{B}T}{\hslash} )( \frac{\alpha\Delta}{\eta} )( {1 + \frac{N_{z}}{2( {N_{y} - N_{z}} )}} )\mspace{265mu}(2)}$Perpendicular  magnetization$\Delta = {\frac{KV}{k_{B}T} - {\frac{\mu_{0}{Ms}^{2}V}{2k_{B}T}( {N_{y} - N_{x}} )\mspace{335mu}\text{(3)}}}$$I_{c0} = {( \frac{4{ek}_{B}T}{\hslash} )( \frac{\alpha\Delta}{\eta} )\mspace{455mu}(4)}$

In equations (1) to (4),

K: magnetic anisotropy energy density of an easy axis direction, μ₀:space permeability, Ms: saturated magnetization amount, V: volume,k_(B): Boltzmann's constant, T: temperature, (Nx, Ny, Nz): diamagneticcoefficient, α: damping coefficient, η: spin polarizability, e: chargeof electron, h with a bar: converted Plank's constant.

The subscripts (x, y, z) of the diamagnetic coefficient representdirections of a three-dimensional space, and (x, y) represent anin-laminated-plane direction and z represents a direction perpendicularto the laminated plane.

Δ is defined by a ratio of an energy necessary for inverting themagnetization direction of the memory layer (hereinafter, referred to asan energy barrier), and thermal energy.

In the in-plane magnetization type, the magnetic anisotropy energydensity K is negligibly small, and Δ is predominantly determined by asecond term of equation (1).

To secure Δ equal to or greater than 0, it is necessary to make Ny>Nx.Therefore, a shape in (x, y) plane of the memory layer may be anelliptical shape or a rectangular shape.

Here, (a length in a y direction)<(a length in an x direction). Anenergy barrier obtained in this manner, is referred to as a shapemagnetic anisotropy energy. The shape magnetic anisotropy isproportional to the square of the saturated magnetization Ms.

On the other hand, in the perpendicular magnetization type, it isnecessary for the anisotropy energy density K to be large to some degreeso as to secure Δ equal to or greater than 0.

Generally, an energy derived from a crystal structure of the magneticlayer, which is called crystal magnetic anisotropy, is used.

A second term of the equation (3) is called a diamagnetic term andfunctions to diminish Δ.

In addition, it is not necessary to use the shape anisotropy energy inthe perpendicular magnetization type, such that a shape in (x, y) planeof the memory layer 17 is frequently made to be a circular shape or asquare shape. At this time, Ny=Nx.

In another type of the perpendicular magnetization type, even when thecrystal magnetic anisotropy is not provided to the magnetic layeritself, an interface magnetic anisotropy working at an interface with anadjacent layer is used.

Here, when the interface magnetic anisotropy energy per unit area is setto Ki, K=Ki/t. Here, t is a film thickness of a magnetic layer. From theequation of Δ, the energy barrier E per unit area is as follows.

$\begin{matrix}{{Math}.\mspace{14mu} 2} & \; \\{E = {K_{i} - \frac{\mu_{0}{Ms}^{2}t}{2}}} & (5)\end{matrix}$

In addition, it is set that Nz−Nx=1 for simplicity. A second term of theequation (5) is a diamagnetic field energy.

In addition, E>0 is a perpendicular magnetization condition. From this,the smaller the film thickness, the more easily the perpendicularmagnetization occurs.

In the case of using the interface magnetic anisotropy, the saturatedmagnetization amount Ms and the interface magnetic anisotropy energy Kiitself depend on the film thickness, such that it is necessary to thefilm thickness satisfying E>0 of the equation (5) such that the memorylayer 17 or the magnetization-fixed layer 15 is perpendicularlymagnetized.

Therefore, in this embodiment, the memory layer 17 and themagnetization-fixed layer 15, which are ferromagnetic layers, are set tohave the energy barrier E per unit area satisfying E>0.

In addition, in this embodiment, a magnitude of an effective diamagneticfield which the memory layer 17 receives is set to be smaller than asaturated magnetization amount of the memory layer 17.

The index Δ of the thermal stability and the threshold value Ic of thecurrent are often in a trade-off relationship. Therefore, compatibilityof these becomes an issue to retain the memory characteristic.

In regard to the threshold value of the current that changes themagnetization state of the memory layer, actually, for example, in a TMRelement in which the thickness of the memory layer 17 is 2 nm, and aplanar pattern is substantially an elliptical shape of 100 nm×150 nm, athreshold value+Ic of a positive side is +0.5 mA, a threshold value−Icof a negative side is −0.3 mA, and a current density at this time issubstantially 3.5×10⁶ A/cm².

On the contrary, in a common MRAM that performs magnetization inversionusing a current magnetic field, the write current of several mA or moreis necessary.

Therefore, in the case of performing magnetization inversion by spininjection, the threshold value of the above-described write currentbecomes sufficiently small, such that this is effective for diminishingpower consumption of an integrated circuit.

In addition, an interconnect (interconnect 105 of FIG. 13) for thegeneration of the current magnetic field, which is necessary for acommon MRAM, is not necessary, such that in regard to the degree ofintegration, it is advantageous compared to the common MRAM.

In the case of performing magnetization inversion by spin injection,since the writing (recording) of information is performed by directlyflowing a current to the memory element, to select a memory cell thatperforms the writing, the memory element is connected to a selectiontransistor to construct the memory cell.

In this case, the current flowing to the memory element is restricted toa current magnitude (saturated current of the selection transistor) thatcan be made to flow to the selection transistor.

To make an inversion current Ic₀ of the magnetization by the spininjection smaller than the saturated current of the selectiontransistor, it is effective to diminish the saturated magnetizationamount Ms of the memory layer 17.

However, in the case of simply diminishing the saturated magnetizationamount Ms (for example, U.S. Pat. No. 7,242,045), the thermal stabilityof the memory layer 17 is significantly deteriorated, and therefore itis difficult for the memory element to function as a memory.

To construct the memory, it is necessary that the index Δ of the thermalstability is equal to or greater than a magnitude of a certain degree.

The present inventors have made various studies, and as a resultthereof, they have found that when for example, a composition of Co—Fe—Bis selected as the ferromagnetic layer making up the memory layer 17,the magnitude of the effective diamagnetic field (M_(effective)) whichthe memory layer 17 receives becomes smaller than the saturatedmagnetization amount Ms of the memory layer 17.

By using the above-described ferromagnetic material, the magnitude ofthe effective diamagnetic field which the memory layer 17 receivesbecomes smaller than the saturated magnetization amount Ms of the memorylayer 17.

In this manner, it is possible to make the diamagnetic field which thememory layer 17 receives small, such that it is possible to obtain aneffect of diminishing the inversion current Ic0 expressed by theequation (4) without deteriorating the thermal stability Δ expressed bythe equation (3).

In addition, the present inventors has found that Co—Fe—B magnetizes ina direction perpendicular to a film face within a restricted compositionrange of the selected Co—Fe—B composition, and due to this, it ispossible to secure a sufficient thermal stability even in the case of aextremely minute memory element capable of realizing Gbit classcapacity.

Therefore, in regard to a spin injection-type magnetization inversionmemory, it is possible to make a stable memory in which information maybe written with a low current in a state where the thermal stability issecured.

In this embodiment, it is configured such that the magnitude of theeffective diamagnetic field which the memory layer 17 receives is madeto be less than the saturated magnetization amount Ms of the memorylayer 17, that is, a ratio of the magnitude of the effective diamagneticfield with respect to the saturated magnetization amount Ms of thememory layer 17 becomes less than 1.

In addition, a magnetic tunnel junction (MTJ) element is configured byusing a tunnel insulating layer (insulating layer 16) formed of aninsulating material as the non-magnetic intermediate layer disposedbetween the memory layer 17 and the magnetization-fixed layer 15 inconsideration of the saturated current value of the selectiontransistor.

The magnetic tunnel junction (MTJ) element is configured by using thetunnel insulating layer, such that it is possible to make amagnetoresistance change ratio (MR ratio) large compared to a case wherea giant magnetoresistive effect (GMR) element is configured by using anon-magnetic conductive layer, and therefore it is possible to increaseread-out signal strength.

Particularly, when magnesium oxide (MgO) is used as the material of theintermediate layer 16 as the tunnel insulating layer, it is possible tomake the magnetoresistance change ratio (MR ratio) large compared to acase where aluminum oxide, which can be generally used, is used.

In addition, generally, spin injection efficiency depends on the MRratio, and the larger the MR ratio, the more spin injection efficiencyis improved, and therefore it is possible to diminish magnetizationinversion current density.

Therefore, when magnesium oxide is used as the material of the tunnelinsulating layer 16 and the memory layer 17 is used, it is possible todiminish the threshold write current by spin injection and therefore itis possible to perform the writing (recording) of information with asmall current. In addition, it is possible to increase the read-outsignal strength.

In this manner, it is possible to diminish the threshold write currentby spin injection by securing the MR ratio (TMR ratio), and it ispossible to perform the writing (recording) of information with a smallcurrent. In addition, it is possible to increase the read-out signalstrength.

As described above, in a case where the tunnel insulating layer 16 isformed of the magnesium oxide (MgO) film, it is desirable that the MgOfilm be crystallized and therefore a crystal orientation be maintainedin (001) direction.

In addition, in this embodiment, in addition to a configuration formedof a magnesium oxide, an intermediate layer (tunnel insulating layer 16)disposed between the memory layer 17 and the magnetization-fixed layer15 may be configured by using, for example, various insulatingmaterials, dielectric materials, and semiconductors such as aluminumoxide, aluminum nitride, SiO₂, Bi₂O₃, MgF₂, CaF, SrTiO₂, AlLaO₃, andAl—N—O.

An area resistance value of the tunnel insulating layer 16 is necessaryto be controlled to several tens Ωμm2 or less in consideration of theviewpoint of obtaining a current density necessary for inverting themagnetization direction of the memory layer 17 by spin injection.

In the tunnel insulating layer 16 formed of the MgO film, to retain thearea resistance value within the above-described range, it is necessaryto set the film thickness of the MgO film to 1.5 nm or less.

In addition, it is desirable to make the memory element small to easilyinvert the magnetization direction of the memory layer 17 with a smallcurrent.

Therefore, preferably, the area of the memory element is set to 0.01 μm2or less.

In addition, in this embodiment, the memory layer 17 may be formed bydirectly laminating another ferromagnetic layer having a differentcomposition. In addition, a ferromagnetic layer and a soft magneticlayer may be laminated, or a plurality of ferromagnetic layers may belaminated through a soft magnetic layer or a non-magnetic layerinterposed therebetween. Even in the case of laminating in this manner,an effect may be obtained.

Particularly, in a case where the memory layer 17 is configured bylaminating the plurality of ferromagnetic layers through thenon-magnetic layer, it is possible to adjust the strength of interactionbetween the ferromagnetic layers, such that even when the dimensions ofthe memory element are under sub-micron, there is obtained an effect ofcontrolling magnetization inversion current so that it does not becomelarge. As a material of the non-magnetic layer in this case, Ru, Os, Re,Ir, Au, Ag, Cu, Al, Bi, Si, B, C, Cr, Ta, Pd, Pt, Zr, Hf, W, Mo, Nb, oran alloy thereof may be used.

Other configuration of the memory element may be the same as theconfiguration of a memory element that records information by the spininjection in the related art.

The magnetization-fixed layer 15 may be configured in such a manner thatthe magnetization direction is fixed by only a ferromagnetic layer or byusing an anti-ferromagnetic combination of an anti-ferromagnetic layerand a ferromagnetic layer.

In addition, the magnetization-fixed layer 15 may be configured by asingle layer of a ferromagnetic layer, or a ferri-pin structure in whicha plurality of ferromagnetic layers are laminated through a non-magneticlayer.

As a material of the ferromagnetic layer making up themagnetization-fixed layer 15 of the laminated ferri-pin structure, Co,CoFe, CoFeB, or the like may be used. In addition, as a material of thenon-magnetic layer, Ru, Re, Ir, Os, or the like may be used.

As a material of the anti-ferromagnetic layer, a magnetic material suchas an FeMn alloy, a PtMn alloy, a PtCrMn alloy, an NiMn alloy, an IrMnalloy, NiO, and Fe₂O₃ may be exemplified.

In addition, a magnetic characteristic may be adjusted by adding anon-magnetic element such as Ag, Cu, Au, Al, Si, Bi, Ta, B, C, O, N, Pd,Pt, Zr, Hf, Ir, W, Mo, and Nb to the above-describe magnetic materials,or in addition to this, various physical properties such as acrystalline structure, a crystalline property, a stability of asubstance, or the like may be adjusted.

In addition, in relation to a film configuration of the memory element,the memory layer 17 may be disposed at the lower side of themagnetization-fixed layer 15, or at the upper side thereof, and in anydisposition, there is no problem at all.

In addition, there is no problem at all in a case where themagnetization-fixed layer 15 is disposed at the upper side and the lowerside of the memory layer 17, so-called dual-structure.

In addition, as a method of reading-out information recorded in thememory layer 17 of the memory element, a magnetic layer that becomes areference for the information is provided on the memory layer 17 of thememory element through a thin insulating film, and the reading-out maybe performed by a ferromagnetic tunnel current flowing through theinsulating layer 16, or the reading-out may be performed by amagnetoresistive effect.

2. Configuration of Embodiment

Subsequently, a specific configuration of this embodiment will bedescribed.

As an embodiment, a schematic configuration diagram (perspective view)of a memory device is shown in FIG. 1.

This memory device includes a memory element 3, which can retaininformation at a magnetization state, disposed in the vicinity of anintersection of two kinds of address interconnects (for example, a wordline and a bit line) that are perpendicular to each other.

Specifically, a drain region 8, a source region 7, and a gate electrode1 that make up a selection transistor that selects each memory cell areformed in a portion separated by an element separation layer 2 of asemiconductor substrate 10 such as a silicon substrate, respectively.Among them, the gate electrode 1 also functions as one side addressinterconnect (for example, a word line) that extends in the front-backdirection in the drawing.

The drain region 8 is formed commonly with left and right selectiontransistors in the drawing, and an interconnect 9 is connected to thedrain region 8.

The memory element 3 is disposed between the source region 7, and theother side address interconnect (for example, a bit line) 6 that isdisposed at the upper side and extends in the left-right direction inthe drawing. This memory element 3 has a memory layer including aferromagnetic layer whose magnetization direction is inverted by spininjection.

In addition, the memory element 3 is disposed in the vicinity of anintersection of two kinds of address interconnects 1 and 6.

The memory element 3 is connected to the bit line 6 and the sourceregion 7 through upper and lower contact layers 4, respectively.

In this manner, a current flows into the memory element 3 in theperpendicular direction thereof through the two kind of addressinterconnects 1 and 6, and the magnetization direction of the memorylayer may be inverted by a spin injection.

In addition, a cross-sectional view of the memory element 3 of thememory device according to this embodiment is shown in FIG. 2.

As shown in FIG. 2, in the memory element 3, an underlying layer 14, themagnetization-fixed layer 15, the insulating layer 16, the memory layer17, and the cap layer 18 are laminated in this order from a lower layerside.

In this case, the magnetization-fixed layer 15 is provided at a lowerlayer in relation to a memory layer 17 in which the magnetizationdirection of magnetization M17 is inverted by a spin injection.

In regard to the spin injection type memory, “0” and “1” of informationare defined by a relative angle between the magnetization M17 of thememory layer 17 and magnetization M15 of the magnetization-fixed layer15.

An insulating layer 16 that serves as a tunnel barrier layer (tunnelinsulating layer) is provided between the memory layer 17 and themagnetization-fixed layer 15, and therefore an MTJ element is configuredby the memory layer 17 and the magnetization-fixed layer 15.

In addition, an underlying layer 14 is formed under themagnetization-fixed layer 15, and a cap layer 18 is formed on the memorylayer 17.

The memory layer 17 is formed of a ferromagnetic material having amagnetic moment in which the direction of the magnetization M17 isfreely changed in a direction perpendicular to a film face.

The magnetization-fixed layer 15 is formed of a ferromagnetic materialhaving a magnetic moment in which the magnetization M15 is fixed in thedirection perpendicular to the film face.

The storage of information is performed by the magnetization directionof the memory layer 17 having a unidirectional anisotropy. The writingof information is performed by applying a current in the directionperpendicular to the film face and by causing a spin torquemagnetization inversion. In this way, the magnetization-fixed layer 15is provided at a lower layer in relation to the memory layer 17 in whichthe magnetization direction is inverted by the spin injection, andserves as a reference for the memory information (magnetizationdirection) of the memory layer 17.

In this embodiment, Co—Fe—B is used for the memory layer 17 and themagnetization-fixed layer 15.

In addition, the memory layer 17 and the magnetization-fixed layer 15are formed to have a film thickness in such a manner that the energybarrier E per unit area is larger than zero, that is, E>0.

The magnetization-fixed layer 15 serves as the reference for theinformation, such that it is necessary that the magnetization directiondoes not vary, but it is not necessarily necessary to be fixed in aspecific direction. The magnetization-fixed layer 15 may be configuredin such a manner that migration becomes more difficult than in thememory layer 17 by making a coercive force large, by making the filmthickness large, or by making a damping constant large compared to thememory layer 17.

In the case of fixing the magnetization, an anti-ferromagnetic materialsuch as PtMn and IrMn may be brought into contact with themagnetization-fixed layer 15, or a magnetic material brought intocontact with such an anti-ferromagnetic material may be magneticallycombined through a non-magnetic material such as Ru, and thereby themagnetization-fixed layer 15 may be indirectly fixed.

In this embodiment, particularly, a composition of the memory layer 17of the memory element 3 is adjusted such that a magnitude of aneffective diamagnetic field which the memory layer 17 receives becomessmaller than the saturated magnetization amount Ms of the memory layer17.

That is, a composition of a ferromagnetic material Co—Fe—B of the memorylayer 17 is selected, and the magnitude of the effective diamagneticfield which the memory layer 17 receives is made to be small, such thatthe magnitude of the effective diamagnetic field becomes smaller thanthe saturated magnetization amount Ms of the memory layer 17.

In addition, in this embodiment, in a case where the insulating layer 16that is an intermediate layer is formed of a magnesium oxide (MgO)layer. In this case, it is possible to make a magnetoresistive changeratio (MR ratio) high.

When the MR ratio is made to be high as described above, the spininjection efficiency is improved, and therefore it is possible todiminish a current density necessary for inverting the direction of themagnetization M17 of the memory layer 17.

The memory element 3 of this embodiment can be manufactured bycontinuously forming from the underlying layer 14 to the cap layer 18 ina vacuum apparatus, and then by forming a pattern of the memory element3 by a processing such as a subsequent etching or the like.

According to the above-described embodiment, the memory layer 17 of thememory element 3 is configured in such a manner that the magnitude ofthe effective diamagnetic field that the memory layer 17 receives issmaller than the saturated magnetization amount Ms of the memory layer17, such that the diamagnetic field that the memory layer 17 receives isdecreased, and it is possible to diminish an amount of the write currentnecessary for inverting the direction of the magnetization M17 of thememory layer 17.

On the other hand, since the amount of the write current may bediminished even when the saturated magnetization amount Ms of the memorylayer 17 is not diminished, it is possible to sufficiently secure thesaturated magnetization amount of the memory layer 17 and therefore itis possible to sufficiently secure the thermal stability of the memorylayer 17.

In addition, in this embodiment, the memory layer 17 and themagnetization-fixed layer 15 are set to have the energy barrier E perunit area satisfying E>0.

When the film thickness of the memory layer 17 and themagnetization-fixed layer 15 is within a predetermined range satisfyingE>0, the interface magnetic anisotropy energy is larger than thediamagnetic field energy. At this time, the easy axis of magnetizationof the memory layer 17 and the magnetization-fixed layer 15 becomes aperpendicular direction with respect to a laminated face. Therefore, itis possible to decrease an inversion current of the memory elementcompared to a case where the easy axis of the magnetization is anin-plane direction.

In this manner, the securing of sufficient thermal stability that is aninformation retaining ability, and the decrease in the magnetizationinversion current (write current) can be compatible with each other,such that it is possible to configure the memory element 3 excellent ina characteristic balance. In this manner, an operation error is removedand an operation margin of the memory element 3 is sufficientlyobtained, such that it is possible to stably operate the memory element3.

Accordingly, it is possible to realize a memory that stably operateswith high reliability.

In addition, the write current is diminished, such that it is possibleto diminish the power consumption when performing the writing into thememory element 3. Therefore, it is possible to diminish the powerconsumption of the entirety of the memory device in which a memory cellis configured by the memory element 3 of this embodiment.

Therefore, in regard to the memory device including the memory element 3capable of realizing a memory device that is excellent in theinformation retaining ability, has high reliability, and operatesstably, it is possible to diminish the power consumption in a memorydevice including the memory element 3.

In addition, the memory device that includes a memory element 3 shown inFIG. 2 and has a configuration shown in FIG. 1 has an advantage in thata general semiconductor MOS forming process may be applied when thememory device is manufactured.

Therefore, it is possible to apply the memory device of this embodimentas a general purpose memory.

3. Experiment

Here, in regard to the configuration of the memory element of thisembodiment, by specifically selecting the material of the ferromagneticlayer making up the memory layer 17, the magnitude of the effectivediamagnetic field that the memory layer 17 receives was adjusted, andthereby a sample of the memory element was manufactured, and thencharacteristics thereof was examined.

In addition, an experiment on an appropriate film thickness of thememory layer 17 and the magnetization-fixed layer 15 that areferromagnetic layers.

In an actual memory device, as shown in FIG. 1, a semiconductor circuitfor switching or the like present in addition to the memory element 3,but here, the examination was made on a wafer in which only the memoryelement is formed for the purpose of examining the magnetizationinversion characteristic of the memory layer 17.

In addition, in the following experiments 1 to 4, investigation is madeinto a configuration where a magnitude of the effective diamagneticfield which the memory layer 17 receives is made to be small, andthereby the magnitude of an effective diamagnetic field which the memorylayer 17 receives is smaller than a saturated magnetization amount ofthe memory layer, by selecting a composition of the ferromagneticmaterial, that is, Co—Fe—B of the memory layer 17.

In addition, in experiments 5 to 8, investigation is made into anappropriate film thickness of the memory layer 17 and themagnetization-fixed layer 15.

Experiment 1

A thermal oxide film having a thickness of 300 nm was formed on asilicon substrate having a thickness of 0.725 mm, and the memory element3 having a configuration shown in FIG. 2 was formed on the thermal oxidefilm.

Specifically, in regard to the memory element 3 shown in FIG. 2, amaterial and a film thickness of each layer were selected as describedbelow.

-   -   Underlying layer 14: Laminated film of a Ta film having a film        thickness of 10 nm and a Ru film having a film thickness of 25        nm    -   Magnetization-fixed layer 15: CoFeB film having a film thickness        of 2.5 nm    -   Tunnel insulating layer 16: Magnesium oxide film having a film        thickness of 0.9 nm    -   Memory layer 17: CoFeB film having the same composition as that        of the magnetization-fixed layer    -   Cap layer 18: Laminated film of a Ta film having a film        thickness of 3 nm, a Ru film having a thickness of 3 nm, and a        Ta film having a thickness of 3 nm

Each layer was selected as described above, a Cu film (not shown) havinga film thickness of 100 nm (serving as a word line described below) wasprovided between the underlying layer 14 and the silicon substrate.

In the above-described configuration, the ferromagnetic layer of thememory layer 17 was formed of a ternary alloy of Co—Fe—B, and a filmthickness of the ferromagnetic layer was fixed to 2.0 nm.

Each layer other than the insulating layer 16 formed of a magnesiumoxide film was formed using a DC magnetron sputtering method.

The insulating layer 16 formed of the magnesium oxide (MgO) film wasformed using a RF magnetron sputtering method.

In addition, after forming each layer of the memory element 3, a heatingtreatment was performed in a magnetic field heat treatment furnace.

Next, after masking a word line portion by a photolithography, aselective etching by Ar plasma was performed with respect to a laminatedfilm other than the word line portion, and thereby the word line (lowerelectrode) was formed.

At this time, a portion other than the word line was etched to the depthof 5 nm in the substrate.

Then, a mask of a pattern of the memory element 3 by an electron beamdrawing apparatus was formed, a selective etching was performed withrespect to the laminated film, and thereby the memory element 3 wasformed. A portion other than the memory element 3 was etched to aportion of the word line immediately over the Cu layer.

In addition, in the memory element for the characteristic evaluation, itis necessary to make a sufficient current flow to the memory element soas to generate a spin torque necessary for magnetization inversion, suchthat it is necessary to suppress the resistance value of the tunnelinsulating layer. Therefore, a pattern of the memory element 3 was setto an elliptical shape having a short axis of 0.09 μm×a long axis of0.18 μm, and an area resistance value (Ωμm²) of the memory element 3 wasset to 20 Ωμm².

Next, a portion other than the memory element 3 was insulated bysputtering Al₂O₃ to have a thickness of substantially 100 nm.

Then, a bit line serving as an upper electrode and a measurement padwere formed by using photolithography.

In this manner, a sample of the memory element 3 was manufactured.

By the above-described manufacturing method, each sample of the memoryelement 3 in which a composition of Co—Fe—B alloy of the ferromagneticlayer of the memory layer 17 was changed was manufactured.

In the composition of the Co—Fe—B alloy, a composition ratio of CoFe andB was fixed to 80:20, and a composition ratio of Co in CoFe, that is,x(atomic %) was changed to 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, 10%,and 0%.

With respect to each sample of the memory element 3 manufactured asdescribed above, a characteristic evaluation was performed as describedbelow.

Before the measurement, it was configured to apply a magnetic field tothe memory element 3 from the outside to control an inversion current insuch a manner that a value in a positive direction and a value in anegative direction to be symmetric to each other.

In addition, a voltage applied to the memory element 3 was set up to 1 Vwithin a range without breaking down the insulating layer 16.

Measurement of Saturated Magnetization Amount

Saturated magnetization amount Ms was measured by a VSM measurementusing a Vibrating Sample Magnetometer.

Measurement of Effective Diamagnetic Field

As a sample for measuring an effective diamagnetic field, in addition tothe above-described sample of the memory element 3, a sample in whicheach layer making up the memory element 3 was formed was manufacturedand then the sample was processed to have a planar pattern of 20 mm×20mm square.

In addition, a magnitude M_(effective) of an effective diamagnetic fieldwas obtained by FMR (Ferromagnetic Resonance) measurement.

A resonance frequency fFMR, which is obtained by the FMR measurement,with respect to arbitrary external magnetic field H_(ex) is given by thefollowing equation (6).Math. 3f _(FMR)=γ′√{square root over (4πM _(effective)(H _(K) +H _(ex)))}  (6)

Here, M_(effective) in the equation (6) may be expressed by4πM_(effective)=4πMs−H⊥(H⊥: anisotropy field in a directionperpendicular to a film face).

Measurement of Inversion Current Value and Thermal Stability

An inversion current value was measured for the purpose of evaluatingthe writing characteristic of the memory element 3 according to thisembodiment.

A current having a pulse width of 10 μs to 100 ms is made to flow to thememory element 3, and then a resistance value of the memory element 3was measured.

In addition, the amount of current that flows to the memory element 3was changed, and then a current value at which a direction of themagnetization M17 of the memory layer 17 of the memory element 3 wasinverted was obtained. A value obtained by extrapolating a pulse widthdependency of this current value to a pulse width 1 ns was set to theinversion current value.

In addition, the inclination of a pulse width dependency of theinversion current value corresponds to the above-described index Δ ofthe thermal stability of the memory element 3. The less the inversioncurrent value is changed (the inclination is small) by the pulse width,the more the memory element 3 is strengthened against thermaldisturbance.

In addition, twenty memory elements 3 with the same configuration weremanufactured to take variation in the memory element 3 itself intoconsideration, the above-described measurement was performed, and anaverage value of the inversion current value and the index Δ of thethermal stability were obtained.

In addition, an inversion current density Jc0 was calculated from theaverage value of the inversion current value obtained by the measurementand an area of the planar pattern of the memory element 3.

In regard to each sample of the memory element 3, a composition ofCo—Fe—B alloy of the memory layer 17, measurement results of thesaturated magnetization amount Ms and the magnitude M_(effective) of theeffective diamagnetic field, and a ratio M_(effective)/MS of effectivediamagnetic field to the saturated magnetization amount were shown inTable 1. Here, an amount of Co of Co—Fe—B alloy of the memory layer 17described in Table 1 was expressed by an atomic %.

TABLE 1 Ms(emu/cc) Meffctive(emu/cc) Meffective/Ms (Co₉₀Fe₁₀)₈₀—B₂₀ 9601210 1.26 (Co₈₀Fe₂₀)₈₀—B₂₀ 960 1010 1.05 (Co₇₀Fe₃₀)₈₀—B₂₀ 1040 900 0.87(Co₆₀Fe₄₀)₈₀—B₂₀ 1200 830 0.69 (Co₅₀Fe₅₀)₈₀—B₂₀ 1300 690 0.53(Co₄₀Fe₆₀)₈₀—B₂₀ 1300 500 0.38 (Co₃₀Fe₇₀)₈₀—B₂₀ 1260 390 0.31(Co₂₀Fe₈₀)₈₀—B₂₀ 1230 360 0.29 (Co₁₀Fe₉₀)₈₀—B₂₀ 1200 345 0.29 Fe₈₀—B₂₀1160 325 0.28

From the table 1, in a case where the amount x of Co in(Co_(x)Fe_(100-x))₈₀B₂₀ was 70% or less, the magnitude of the effectivediamagnetic field (M_(effective)) was smaller than the saturatedmagnetization amount Ms, that is, the ratio of M_(effective)/Ms in acase where the amount x of Co was 70% or less became a value less than1.0.

In addition, it was confirmed that the more the amount x of Codecreased, the larger the difference between M_(effective) and Ms.

A measurement result of the inversion current value was shown in FIG. 3,and a measurement result of the index of the thermal stability was shownin FIG. 4.

FIG. 3 shows a relationship between the amount x (content in CoFe;atomic %) of Co in the Co—Fe—B alloy of the memory layer 17 and theinversion current density Jc0 obtained from the inversion current value.

FIG. 4 shows a relationship between an amount x (content in CoFe; atomic%) of Co in the Co—Fe—B alloy of the memory layer 17 and the index Δ ofthe thermal stability.

As can be seen from FIG. 3, as the amount x of Co decreases, theinversion current density Jc0 decreases.

This is because in a case where the amount x of Co becomes small, thesaturated magnetization amount Ms increases, but the effectivediamagnetic field M_(effective) decreases, and therefore the product ofthem Ms×M_(effective) becomes small.

As can be seen from FIG. 4, as the amount x of Co decreased, the index Δof the thermal stability increased, and in a case where the amount x ofCo became more or less small to a degree, the index Δ of the thermalstability became stable to a large value.

This well corresponds to a change that is expected from the measurementresult of the saturated magnetization amount Ms shown in Table 1 and atendency where the index Δ of the thermal stability from the equation(2) is proportional to the saturated magnetization amount Ms.

As was clear from the results of Table 1, FIGS. 4 and 5, in acomposition where the amount x of Co was 70% or less and the effectivediamagnetic field M_(effective) was less than the saturatedmagnetization amount Ms, it was possible to diminish the inversioncurrent value Jc0 with a high thermal stability retained, without usinga method in which Ms was decreased and therefore the thermal stabilitywas sacrificed.

Experiment 2

As can be seen from the experiment 1, in the case of(Co_(x)Fe_(100-x))₈₀B₂₀, it was possible to diminish the inversioncurrent value Jc0 with a high thermal stability retained in acomposition where the amount x of Co was 70% or less.

Therefore, in experiment 2, an effect on a ratio of Co and Fe, and theM_(effective)/Ms, which was caused by an amount of B, was examined byusing a memory layer 17 having a composition (CO₇₀Fe₃₀)₈₀B_(z) and acomposition (CO₈₀Fe₂₀)₈₀B_(z). The details of a sample weresubstantially the same as those in the experiment 1.

Table 2 shows compositions of CoFeB in which the amount of B (atomic %)was set to 5 to 40% in (CO₇₀Fe₃₀)_(100-Z)B_(z), results of measurementof the saturated magnetization amount Ms and the magnitude M_(effective)of the effective diamagnetic field, and a ratio M_(effective)/Ms of thesaturated magnetization amount and the magnitude of the effectivediamagnetic field.

In addition, Table 3 shows compositions of CoFeB in which the amount ofB (atomic %) was similarly set to 5 to 40% in (CO₅₀Fe₂₀)_(100-z)B_(z),and a ratio M_(effective)/Ms of the saturated magnetization amount andthe magnitude M_(effective) of the effective diamagnetic field.

TABLE 2 Ms(emu/cc) Meffective(emu/cc) Meffective/Ms (Co₇₀Fe₃₀)₉₅—B₅ 13101090 0.83 (Co₇₀Fe₃₀)₉₀—B₁₀ 1250 1080 0.89 (Co₇₀Fe₃₀)₈₀—B₂₀ 1040 900 0.87(Co₇₀Fe₃₀)₇₀—B₃₀ 820 730 0.89 (Co₇₀Fe₃₀)₆₀—B₄₀ 450 690 1.53

TABLE 3 Ms(emu/cc) Meffective(emu/cc) Meffective/Ms (Co₈₀Fe₂₀)₉₅—B₅ 12501280 1.02 (Co₈₀Fe₂₀)₉₀—B₁₀ 1100 1140 1.04 (Co₈₀Fe₂₀)₈₀—B₂₀ 960 1010 1.05(Co₈₀Fe₂₀)₇₀—B₃₀ 750 890 1.19 (Co₈₀Fe₂₀)₆₀—B₄₀ 430 690 1.60

From the results of Table 2, it can be confirmed that in a case wherethe ratio of Co and Fe was set to 70/30 like (CO₇₀Fe₃₀)_(100-Z)B_(z),the magnitude M_(effective) of the effective diamagnetic field wassmaller than the saturated magnetization amount Ms in compositions otherthan a composition where the amount z of B was 40 atomic %.

From the results of Table 3, it could be confirmed that in a case wherethe ratio of Co and Fe was set to 80/20 like (CO₈₀Fe₂₀)_(100-Z)B_(z),the magnitude M_(effective) of the effective diamagnetic field waslarger than the saturated magnetization amount Ms in all compositions.

From the results of the above-described Tables 1 to 3, it was revealedthat in a case where the amount z of B is within a range of 30 atomic %or less, a magnitude correlation of the saturated magnetization amountMs and the magnitude M_(effective) of the effective diamagnetic field isdetermined by the ratio of Co and Fe.

Therefore, a composition of the Co—Fe—B alloy where the magnitudeM_(effective) of the effective diamagnetic field is smaller than thesaturated magnetization amount Ms is as follows:(CO_(x)—Fe_(y))100_(−z)-B_(z),Here, 0≦Co_(x)≦70,30≦Fe_(y)≦100,0<B_(z)≦30.

Experiment 3

In a spin injection type memory of Gbit class, it was assumed that thesize of the memory element is 100 nmφ. Therefore, in experiment 3, thethermal stability was evaluated by using a memory element having thesize of 50 nmφ.

In the composition of Co—Fe—B alloy, a composition ratio (atomic %) ofCoFe and B was fixed to 80:20, and a composition ratio x (atomic %) ofCo in CoFe was changed to 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, 10%,and 0%.

The details of the sample other than the sample size were substantiallythe same as those in the experiment 1.

In a case where the size of the memory element 3 was 50 nmφ, arelationship between an amount of Co (content in CoFe; atomic %) in theCo—Fe—B alloy, and the index Δ of the thermal stability were shown inFIG. 5.

As can be seen from FIG. 5, when the element size was 50 nmφ, Co—Fe—Balloy composition dependency of the thermal stability index Δ waslargely varied from the Co—Fe—B alloy composition dependency of Δobtained in the elliptical memory element having a short axis of 0.09μm×a long axis of 0.18 μm shown in FIG. 4.

According to FIG. 5, the high thermal stability was retained only in thecase of Co—Fe—B alloy composition where Fe is 60 atomic % or more.

As a result of various reviews, it was clear that the reason why theCo—Fe—B alloy containing Fe of 60 atomic % or more shows the highthermal stability Δ in the extremely minute memory element was revealedto be because the magnetization of the Co—Fe—B alloy faced a directionperpendicular to a film face.

The reason why the magnetization of the Co—Fe—B alloy faces thedirection perpendicular to the film face is considered to be because ofa composition in which the effective diamagnetic field M_(effective) issignificantly smaller than the saturated magnetization amount Ms.

In addition, the reason why the thermal stability is secured even in thecase of the extremely minute element of a perpendicular magnetizationfilm is related to the effective anisotropy field, and the effectiveanisotropy field of the perpendicular magnetization film becomes a valuesignificantly larger than that in the in-plane magnetization film. Thatis, in the perpendicular magnetization film, due to an effect of largeeffective anisotropy field, it is possible to maintain a high thermalstability (Δ) even in the case of the extremely minute element notcapable of securing a sufficient thermal stability (Δ) in the in-planemagnetization film.

From the above-described experiment results, in regard to the Co—Fe—Balloy having a composition of (Co_(x)Fe_(100-x))₈₀B₂₀, in a case wherethe amount of Fe_(100-x) is 60% or more, this alloy may be said to besuitable for the memory device of Gbit class using the spin injection.

Experiment 4

As can be seen from the above-described experiment 3, in a case theamount of F was 60 or more in the Co—Fe—B alloy having a composition of(Co_(x)Fe_(100-x))₈₀B₂₀, this alloy was suitable for the memory deviceof Gbit class using the spin injection. In experiment 4, a memoryelement having the size of 50 nmφ was manufactured using the Co—Fe—Balloy containing B in an amount of 5 to 30 atomic %, and the thermalstability was evaluated.

The details other than the element size were substantially the same asthose in the experiment 1.

A relationship between the index Δ of the thermal stability and theCo—Fe—B alloy having a composition (Co_(x)Fe_(100-x))_(100-z)B_(z) inwhich an amount x of Co was 50, 40, 30, 20, 10, and 0, and an amount zof B was 5, 10, 20, and 30 was shown in Table 4.

TABLE 4 (Co₅₀—Fe₅₀)_(100−z)—B_(z) (Co₄₀—Fe₆₀)_(100−z)—B_(z)(Co₃₀—Fe₇₀)_(100−z)—B_(z) (Co₂₀—Fe₈₀)_(100−z)—B_(z)(Co₁₀—Fe₉₀)_(100−z)—B_(z) Fe_(100−z)—B_(z) B_(z) = 5 atomic 19 40 42 4243 44 % B_(z) = 10 atomic 20 41.5 43 44 44 45 % B_(z) = 20 atomic 20 4344 45 46 46 % B_(z) = 30 atomic 21 45 47 48 48 48 %

As can be seen from Table 4, the thermal stability Δ in all compositionsexcept that a case where the amount x of Co was 50, and the amount z ofB was 5 to 30 was maintained to be large.

That is, as is the case with the result of the experiment 4, it wasrevealed that the amount x of Co of 50 and 60 became a boundary line forsecuring the high thermal stability in a extremely minute elementcorresponding to the spin injection type memory of the Gbit class.

Therefore, from the above-described result, it was revealed that theCo—Fe—B alloy of the memory layer 17 was suitable for manufacturing thespin injection type memory of the Gbit class in the followingcomposition:(CO_(x)—Fe_(y))100_(−z)-B_(z),Here, 0≦Co_(x)≦40,60≦Fe_(y)≦100,0<B_(z)≦30.

In addition, in regard to the Co—Fe—B alloy, in a composition where theratio of Fe was great in Co and Fe, the difference between theM_(effective) and Ms becomes large, and this alloy is apt to bemagnetized, and therefore it is easy to secure the thermal stability.

Therefore, in a case where the capacity of the magnetic memory increasesand the size of the memory element 3 decreases, it is easy to secure thethermal stability in the Co—Fe—B alloy containing a large amount of Fe.

Therefore, for example, in consideration of a situation where in whichthe spin injection type magnetic memory of the Gbit class is realized bythe memory layer 17 in which the amount y of Fe is 60, and the sizethereof is 70 nmφ, it is preferable that whenever the diameter of thememory element 3 decreases by 5 nmφ, the amount y of Fe in the Co—Fe—Balloy increase by a value of 5.

For example, in the case of the (CO_(x)—Fe_(y))_(100-z)-B_(z), theamount y of Fe is set in such a manner that an atomic % as a content inCoFe is 65%, 70%, 75%, 80%, . . . (in terms of the amount x of Co, 35%,30%, 25%, 20%, . . . ), and this is a more appropriate example tocorrespond to the size reduction of the memory element.

Experiment 5

Next, experiment was made into an appropriate film thickness of thememory layer 17 and the magnetization-fixed layer 15.

First, in the experiment 5, a thermal oxide film having the thickness of300 nm was formed on a silicon substrate having the thickness of 0.725mm, and a magnetic multi-layered film having a configuration shown inFIG. 6A was formed on this oxide film.

Specifically, in the magnetic multi-layered film, a Ta film (5 nm), anRu film (10 nm), a Ta film (5 nm), a (CO₂₀Fe₈₀)₈₀B₂₀ film (t nm), an Mgfilm (0.15 nm), an MgO film (1 nm), an Mg film (0.15 nm), Ru film (5nm), and a Ta film (5 nm) were formed in this order from an underlyingfilm side.

In addition, after forming the magnetic multi-layered film, a heatingtreatment was performed in a magnetic field heat treatment furnace.

A plurality of samples was manufactured by setting the film thickness tof the (CO₂₀Fe₈₀)₈₀B₂₀ film (t nm) to 0.7 nm, 0.8 nm, 0.9 nm, 1.0 nm,and 1.1 nm, and then each measurement was performed.

In the layer configuration shown in FIG. 6A, one layer of the(CO₂₀Fe₈₀)₈₀B₂₀ film that is a ferromagnetic layer was formed. First, anappropriate film thickness in one ferromagnetic layer was examined.

In addition, in this case, this configuration may be considered as amodel in which the Ta film, the Ru film, and the Ta film correspond tothe underlying layer 14, the (CO₂₀Fe₈₀)₈₀B₂₀ film corresponds to themagnetization-fixed layer 15, and the Mg film, the MgO film, and the Mgfilm correspond to the insulating layer 16.

Measurement of Saturated Magnetization Amount and Anisotropy Field

The saturated magnetization amount Ms and the anisotropy field Hk weremeasured by a VSM measurement using a Vibrating Sample Magnetometer.

A result when the film thickness t of the (Co₂₀Fe₈₀)₈₀B₂₀ film(ferromagnetic film) was 1.0 nm is shown in FIG. 6B.

A solid line corresponds to a case where a magnetic field is appliedperpendicularly to a laminated plane, and a dotted line corresponds to acase where the magnetic field is applied in a plane.

From the fact that the magnetization varies rapidly in the vicinity of azero magnetic field when the magnetic field is applied perpendicularlyto the laminated plane, it can be seen that the perpendicularmagnetization is made.

In a magnetization curve of the in-plane direction, a magnetic field inwhich the magnetization is consistent with the saturated magnetizationis called an anisotropy field Hk. Hk is expressed by the followingequation (7).

$\begin{matrix}{{Math}.\mspace{14mu} 4} & \; \\{H_{k} = {\frac{2K_{i}}{\mu_{0}{Mst}} - {Ms}}} & (7)\end{matrix}$

Therefore, it is possible to obtain the interface magnetic anisotropyenergy Ki per unit area in the equation (5) from the saturatedmagnetization Ms, the anisotropy field Hk, and the film thickness t.

A film thickness dependency of Ki and Ms is shown in FIGS. 7A and 7B.

When the film thickness t is substantially 0.9 nm or more, Ki and Ms areconstant. On the other hand, when the film thickness t is 0.9 nm orless, Ki and Ms decrease substantially in a linear fashion together withthe film thickness t.

Film thickness dependency of an energy barrier E per unit volume inducedfrom FIGS. 7A and 7B is shown in FIG. 7C.

When E>0, the perpendicular magnetization was shown. From this, it canbe seen that when 0.63 nm<t<1.17 nm, the perpendicular magnetization wasmade.

That is, 0.63 nm<t<1.17 nm is a very appropriate range for theferromagnetic layer having the perpendicular magnetization.

However, this condition may be different depending on a composition ofCoFeB and a material of a layer with which the ferromagnetic layer comesinto contact. That is, this thickness range is a range satisfying E>0,and the upper and lower limits of an appropriate numeric range for theferromagnetic layer of the perpendicular magnetization film may varydepending on a condition.

Experiment 6

A Kerr measurement was performed with the film configuration as theexperiment 5. A film configuration is shown in FIG. 8A.

Here, the measurement was performed for each of samples having the filmthickness t of the (CO₂₀Fe₈₀)₈₀B₂₀ film, that is, 0.8 nm, 1.0 nm, 1.2nm, and 1.4 nm.

In addition, as shown in FIG. 8B for comparison, a film configurationwhere an upper film of the (CO₂₀Fe₈₀)₈₀B₂₀ film was substituted with Tahaving the thickness of 5 nm was formed.

A result of the Kerr measurement is shown in FIG. 9A.

When t<1.0 nm, the perpendicular magnetization was shown. It can be seenthat when t=1.2 nm, the collapse of the waveform started and thein-plane magnetization was made. When t=1.4 nm, the in-planemagnetization was completely made. This was substantially consistentwith the result of the experiment 5.

In addition, when observing the energy barrier E per unit volume, E>0 ina case where t=0.8, t=1.0, and t=1.2, and E<0 in a case where t=1.4.

A Kerr measurement with a film configuration shown in FIG. 6B in whichMgO/Ru was substituted with Ta is shown in FIG. 9B. In this case, theperpendicular magnetization was not shown.

From this, it can be seen that it was necessary for the CoFeB film to bebrought into contact with MgO in a single plane to be perpendicularlymagnetized.

Experiment 7

In the above-described experiments 5 and 6, the perpendicular magneticanisotropy of a single layered CoFeB was examined. Actually, an MTJstructure having a layer structure of a ferromagnetic layer/tunnelbarrier layer/ferromagnetic layer is necessary to be used as a spininjection type magnetic memory.

Therefore, as shown in FIG. 10A, a magnetic characteristic of so-calledcoercive force different type MTJ was examined by the same Kerrmeasurement as that of the experiment 6.

In a sample of this case, a Ta film (5 nm), an Ru film (10 nm), a Tafilm (5 nm), a (CO₂₀Fe₈₀)₈₀B₂₀ film (1 nm), an MgO film (1 nm),(CO₂₀Fe₈₀)₈₀B₂₀ film (t nm), a Ta film (5 nm), and an Ru film (5 nm)were formed in this order from an underlying film side.

The film thickness of the lower side CoFeB layer was fixed to 1 nm. Itwas confirmed from the experiment 6 that this configuration has theperpendicular magnetization.

Samples were manufactured by setting the thickness t of the CoFeB layerto 1.2 nm, 1.3 nm, 1.6 nm, and 1.7 nm, and then each measurement wasperformed.

In addition, in this case, in this case, this configuration may beconsidered as a model in which from the lower side, the Ta film, the Rufilm, and the Ta film correspond to the underlying layer 14, the lowerside (CO₂₀Fe₈₀)₈₀B₂₀ film corresponds to the magnetization-fixed layer15, and the MgO film corresponds to the insulating layer 16, the upperside (CO₂₀Fe₈₀)₈₀B₂₀ film corresponds to the memory layer 17, the Tafilm and the Ru film correspond to the cap layer 18.

In addition, the lower side (CO₂₀Fe₈₀)₈₀B₂₀ film may be considered asthe memory layer 17, and the upper side (CO₂₀Fe₈₀)₈₀B₂₀ film may beconsidered as the magnetization-fixed layer 15.

A result of the Kerr measurement is shown in FIG. 10B.

When t=1.2 nm, the magnetization inversion step has only one stage. Thisstage is induced by the lower side CoFeB layer, and indicates that theupper side CoFeB layer is not perpendicularly magnetized.

On the other hand, when t=1.3 nm to 1.6 nm, the magnetization inversionstep has two stages. These stages are induced by the lower side CoFeBlayer, and indicates that both the upper side and lower side CoFeBlayers are perpendicularly magnetized.

When t=1.7 nm, magnetization inversion of the upper side CoFeB layerbecomes smooth, and this represents that the perpendicular magnetizationbecomes weak.

As described above, in regard to the film configuration shown in FIG.10A, it was revealed that the film thickness of the upper side CoFeBlayer was preferably 1.3 nm to 1.6 nm.

In addition, in regard to the energy barrier E per unit volume, whent=1.3 and t=1.6, E>0, and when t=1.2 and t=1.7, E<0.

Experiment 8

It is preferable that among the two ferromagnetic layers that come intocontact with the tunnel barrier layer, the magnetization of one side(magnetization-fixed layer 15) be fixed.

To fix the magnetization, a synthetic pin layer structure utilizing aninterlayer coupling may be used.

Therefore, in regard to a film configuration shown in FIG. 11A, the Kerrmeasurement was performed and a magnetic characteristic was examined.

In this case, in this film configuration, a Ta film (3 nm), an Ru film(25 nm), a Pt film (5 nm), a Co film (1.1 nm), a Ru film (0.8 nm), a(CO₂₀Fe₈₀)₈₀B₂₀ film (1 nm), an Mg film (0.15 nm), an MgO film (1 nm),an Mg film (0.15 nm), (CO₂₀Fe₈₀)₈₀B₂₀ film nm), a Ta film (1 nm), a Rufilm (5 nm), and a Ta film (3 nm) were formed in this order from anunderlying film side.

In this case, this configuration may be considered as a model in whichfrom the lower side, the Ta film and the Ru film correspond to theunderlying layer 14, the Pt film, the Co film, the Ru film, and the(CO₂₀Fe₈₀)₈₀B₂₀ film correspond to the magnetization-fixed layer 15 bythe synthetic pin structure, the Mg film, the MgO film, and the Mg filmcorrespond to the insulating film 16, the (CO₂₀Fe₈₀)₈₀B₂₀ filmcorresponds to the memory layer 17, the Ta film, the Ru film, and the Tafilm correspond to the cap layer 18.

The measurement was performed for each of samples having the filmthickness t of the CoFeB layer, that is, 1.2 nm, 1.3 nm, 1.4 nm, 1.5 nm,1.6 nm, and 1.7 nm.

First, with respect to a case where t=1.4 nm, the Kerr measurement wasperformed within a range of 8 kOe. The result is shown in FIG. 11B.

It is inverted to ±4 kOe except for the inversion in the vicinity of azero magnetic field. The inversion in the vicinity of the zero magneticfield corresponds to an inversion at the upper side CoFeB layer, and theinversion at ±4 kOe corresponds to an inversion at the synthetic pinlayer.

From this result, in a case where the applied magnetic field is 4 kOe orless, the magnetization of actual synthetic pin layer may be regarded tobe fixed.

A measurement result in the vicinity of the zero magnetic field wasshown in FIG. 12.

As can be understood from FIG. 7, in a case where the film thickness tof the upper side CoFeB layer was within a range from 1.3 nm to 1.6 nm,the perpendicular magnetization was realized.

In this case, it was also revealed that the thickness of the upper sideCoFeB was preferably from 1.3 mm to 1.6 mm.

In addition, In addition, when observing the energy barrier E per unitvolume, E>0 in a case where t=1.3 to t=1.6, and E<0 in a case wheret=1.2, and t=1.7.

As can be seen from the results of the above-described experiments 5 to8, when the film thickness of the ferromagnetic layer is designed to bewithin a predetermined range, it is possible to apply the perpendicularmagnetic anisotropy, such that it is possible to allow the easy axis ofthe magnetization of the ferromagnetic layer to be perpendicular to thelaminated plane. Therefore, it is possible to decrease an inversioncurrent of the memory element compared to a case where the easy axis ofthe magnetization is an in-plane direction.

Hereinbefore, the embodiment is described, but the present disclosure isnot limited to the film configuration of the memory element 3illustrated in the above-described embodiment, and it is possible toadopt various layer configurations.

For example, in the embodiment, the Co—Fe—B composition of the memorylayer 17 and the magnetization-fixed layer 15 was made to be the same aseach other, but it is not limited to the above-described embodiment, andvarious configurations may be made without departing from the scope.

In addition, in this embodiment, the underlying layer 14 and the caplayer 18 may be formed of a single material, or may be formed by alaminated structure of a plurality of materials.

In addition, the magnetization-fixed layer 15 may be formed by a singlelayer or may use a laminated ferri-pin structure including twoferromagnetic layers and a non-magnetic layer. In addition, a structurein which anti-ferromagnetic film is applied to the laminated ferri-pinstructure film is possible.

In addition, a film configuration of the memory element may be aconfiguration in which the memory layer 17 is disposed at an upper sideof the magnetization-fixed layer 15 or a configuration in which thememory layer 17 is disposed at an upper side. In addition, this filmconfiguration may be so-called dual structure in which themagnetization-fixed layer 15 is disposed at the upper side and the lowerside of the memory layer 17.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope and without diminishing itsintended advantages. It is therefore intended that such changes andmodifications be covered by the appended claims.

The application is claimed as follows:
 1. A memory element, comprising:a layered structure, wherein the layered structure includes, a memorylayer that has magnetization perpendicular to a film face and amagnetization direction thereof varies corresponding to information, amagnetization-fixed layer that has magnetization that is perpendicularto the film face and becomes a reference for the information stored inthe memory layer, and an insulating layer that is provided between thememory layer and the magnetization-fixed layer and is formed of anon-magnetic layer, an electron that is spin-polarized is injected in alamination direction of the layered structure, and thereby themagnetization direction of the memory layer varies and a recording ofinformation is performed with respect to the memory layer, a magnitudeof an effective diamagnetic field which the memory layer receives issmaller than a saturated magnetization amount of the memory layer, andthe memory layer and the magnetization-fixed layer have a film thicknessin such a manner that an interface magnetic anisotropy energy becomeslarger than a diamagnetic energy.
 2. The memory element according toclaim 1, wherein the film thickness of the memory layer and themagnetization-fixed layer is a film thickness in which an energy barrierE per unit area, which is expressed by E=Ki−(μ₀·Ms²·t)/2, is larger thanzero, that is, E>0, here, Ki is an interface magnetic anisotropy energyper unit area, Ms is a saturated magnetization amount, μ₀ is a spacepermeability, and t is a film thickness.
 3. The memory element accordingto claim 2, wherein the memory layer includes Co—Fe—B.
 4. The memoryelement according to claim 2, wherein the magnetization-fixed layerincludes Co—Fe—B.
 5. A memory device, comprising: a memory element thatretains information through a magnetization state of a magneticmaterial; and two kinds of interconnects that intersect each other,wherein the memory element includes a layered structure including amemory layer that has magnetization perpendicular to a film face and amagnetization direction thereof varies corresponding to information, amagnetization-fixed layer that has magnetization that is perpendicularto the film face and becomes a reference for the information stored inthe memory layer, an insulating layer that is provided between thememory layer and the magnetization-fixed layer and is formed of anon-magnetic layer, and an anti-ferromagnetic layer adjacent to themagnetization-fixed layer at a side opposite to the insulating layerside, an electron that is spin-polarized is injected in a laminationdirection of the layered structure, and thereby the magnetizationdirection varies and a recording of information is performed withrespect to the memory layer, a magnitude of an effective diamagneticfield which the memory layer receives is smaller than a saturatedmagnetization amount of the memory layer, the memory layer and themagnetization-fixed layer have a film thickness in such a manner that aninterface magnetic anisotropy energy becomes larger than a diamagneticenergy, the memory element is disposed between the two kinds ofinterconnects, and a current flows to the memory element in thelamination direction through the two kinds of interconnects, and therebya spin-polarized electron is injected to the memory element.